People widely use Voice over Internet Protocol (VoIP) and other voice data communications applications for communicating their voices over computing networks. VoIP telephony service, for example, allows people in households and businesses that have broadband Internet access to make and receive full duplex calls without a telephone line, telephone service, or a long distance service.
VoIP software allows a user to make calls using a computer instead of using a telephone. If the computer is equipped with a microphone and one or more speakers, the user can use the computer as a hands-free speakerphone. VoIP software may permit full duplex operation so that a user can both speak and listen at the same time, just as when using an ordinary telephone.
In FIG. 1, a woman (not shown) using a desktop computer 100 equipped with speakers 110 and a microphone 120 uses the desktop computer 100 as a hands-free speakerphone.
The microphone 120 captures the woman's words, and software executing on the desktop computer 100 translates her speech into a first signal 160. A network (not shown) carries the first signal 160 to a portable computer 130 that a man (not shown) uses as a speakerphone. The woman's speech carried by the first signal 160 is rendered by integrated speakers 140 in the portable computer. An integrated microphone 150 of the portable computer 130 captures the man's speech, and the portable computer 130 translates his speech into a second signal 170. The network carries the second signal 170 to the desktop computer 100, where the man's speech is rendered by the speakers 110.
Because the VoIP service permits full duplex operation, such that people can listen and speak at the same time, users may encounter acoustic feedback. For example, after the man's speech is captured by the integrated microphone 150, transmitted as the second signal 170, and rendered by the speakers 110, the microphone 120 may re-capture his speech. The first signal 160 will carry his speech back to the portable computer 130 and cause his speech to be re-rendered by the integrated speakers 140. The integrated microphone 150 will again re-capture his speech and transmit it to the desktop computer 100. The continual re-capturing and re-rendering of his speech may cause energy to build in one or more frequency ranges, causing feedback.
To avoid feedback, VoIP users may reduce speaker volume. However, reducing the volume may make it difficult to hear another caller. Users also may reposition their speakers or microphones to attempt to prevent the microphones from re-capturing sounds rendered by the speakers, although this may not solve the problem. Further, a user of a portable computer 130 with integrated speakers 140 and an integrated microphone 150 cannot reposition such devices.